Process for surface finishing of metals

ABSTRACT

A process for the surface finishing of metal in which a metal workpiece of repeating cross-section coated with a lubricant and heated at an elevated temperature is passed through a tandem assembly of a lead die, a cutting tool to remove surface metal, and a finish die to provide a finished workpiece having improved surface characteristics and improved mechanical and physical properties.

United States Patent 1191 Cucuz et a1.

[ PROCESS FOR SURFACE FINISHING OF METALS Inventors: Ranko Cucuz,Griffith, Ind.; Miguel A. Verduzco, Chicago; George Zavodny, Jr., PalosHills, both of 111.

La Salle Steel Company, Hammond, lnd.

Filed: Mar. 23, 1972 Appl. No.: 237,375

Assignee:

52 US. Cl 29/557, 29/424, 29/526.6, 29/DIG. 11, 72/286, 72/341, 90/241), 90/24 R Int. Cl B23p 13/04 Field of Search; 29/557, 424, 526.2, 29/526.6, DIG. 7, DIG. 11; 72/275, 286, 324,

a 341; 90/24 D, 24 E, 24 R References Cited UNITED STATES PATENTS 9/1962Shaw et al. 29/D1G. 11

12/ 1 W1 R E. x7? I 1 Primary Examiner-Charles W. Lanham AssistantExaminerV. A. DiPalma Attorney-McDougall, Hersh & Scott [57] ABSTRACT Aprocess for the surface finishing of metal in which a metal workpiece ofrepeating cross-section coated with a lubricant and heated at anelevated temperature is passed through a tandem assembly of a lead die,a cutting tool to remove surface metal, and a finish die to provide afinished workpiece having improved surface characteristics and improvedmechanical and physical properties.

14 Claims, 2 Drawing Figures PRESTRAIGHTENING I HEATER I HEATER v 1PROCESS FOR SURFACE FINISHING 01F METALS This invention relates to thecold finishing of metals, and more particularly, to the simultaneoussurface re moval and warm or hot drawing of wire, bars, rods and likemetal structures of repeating cross-section in long lengths.

In many cold finishing processes, it is desirable to remove unwantedmetal from the surface of the workpiece prior to processing of theworkpiece in a cold finishing operation.

The tandem arrangement of a lead die, cutter and the finish die asdescribed by Shaw in U.S. Pat. No. 3,157,093 has some desirablecharacteristics. However, it has been found that with a great number ofmetals, as represented by hot rolled carbon and alloy steels, toolsteels, and/or any strain-hardened metals, the material being removed bythe cutter builds up on the cutting edge and this built-up edge replacesthe tool as the cutter of the material. The built-up edge representsworkpiecematerial that has become strain hardened by the work performedin the removal of the chip. The built-up edge appears to become weldedto the cutting edge in such a manner that it is the built-up edge thatdoes the shaving of the softer workpiece material. Be-. cause of thebuilt-up edge formation on the cutting edge, it is difficult to holddimensional stability of the workpiece. In addition, pieces of thebuilt-up edge will periodically leave. the cutter and remain welded ontothe workpiece surface. As a result, an undesirable product having poorsurface finish and poor dimensional characteristics is often obtainedboth before and after the workpiece is drawn through the subsequentdrawing die. Furthermore, the welded pieces of the built-up edge whichperiodically leave the cutter can cause failure of the subsequentdrawing die.

This problem has been faced by Zavodny et al. in U.S. Pat. No.3,168,004. Zavodny used heat to soften the metal in order to avoid orminimize the strain hardness which otherwise-is normally introduced intothe metal being removed by the cutting operation. However, the metalremoval process as described by Zavodny etal. in U.S. Pat. No..3,l68,004employs only one tool,.a cutter. In actual operation, the hot rollworkpiece is passed through the cutter without any additional supportfrom draw dies in front of or in back of the cutter. Furthermore, theworkpiece is normally hot roll material with non symmetric cross-section(due to hot mill tolerances, hot roll is normally out-ofround) whichrequires that'a non-uniform depth of cut be taken in order to remove allof the surface defects that may be present in the hot roll material. Allof these factors, i.e. lack of additional support of the workpiece,non-uniform depth of cut and non-uniform cutting forces, leave room'forfurther improvement in the stability of the process, cutter life andoff-center cutting condition.

It is accordingly an object of the present invention to provide aprocess for metal finishing which is capable of the removal ofundesirable surface imperfections of wires, bars, rods and the likewhile simultaneously improving the physical and mechanical properties ofsuch workpieces.

It is a related object of the invention to provide a metal finishingprocess for the removal of surface imperfections which is capable ofproviding .improved cutting stability and uniformity and improvedsurface finish with closer tolerances and minimum scrap.

It is a further object of the invention to provide a process for metalfinishing in which the cutter life is significantly improved.

Theseand other objects and advantages of the invention will appear morefully hereinafter and, for purposes of illustration and not oflimitation, an embodiment of the invention is shown in the accompanyingdrawings in which:

FIG. It is a schematic illustration of the process of the invention; and

FIG. 2 is a schematic detailed view of the tools used in the processillustrated in FIG. 1.

The concepts of the present invention reside in a process for metalfinishing in which a wire, bar, coil, rod or similar elongated workpieceof repeating crosssection coated with a lubricant and heated issubjected to simultaneous warm or hot drawing and metal removaloperations. The working and metal removal are carried out by passing thehot, lubricated workpiece through a lead or draw die which serves toround or size the hot or warm workpiece to guide and support theworkpiece, and to impart improved physical and mechanical properties tothe workpiece.

' After passage through the lead die, the workpiece is passed through acutting or shaving tool which circumscribes the workpiece to effectremoval of surface metal to eliminate surface imperfections. Afterpassage through the cutting tool, the workpiece is again coated with alubricant and passed through a finishing die to size and polish theworkpiece.

It has been found that workpieces processed in ac cordance with thepractice of the invention have substantially improved surface finishesas well as improved mechanical and physical properties. In addition, thestability and uniformity of the cutting or shaving operation issubstantially improved, with essentially no offcenter cutting, toprovide closer tolerances, improved tool life and minimum scrap.

Referring now to the drawings, there is shown in FIG. 1 a schematicdiagram illustrating the process of the invention as applied in theprocessing of wire, it being understood that other metal workpiecehaving a repeating cross-section are similarly processed. A wire 10 froma spool or the like (not shown in the drawing) is first passed through aprestraightener, if desired, and is then coated with the'lubricant, asby spraying with a nozzle M connected to a source of lubricant 16.

The lubricant found to provide best results in the practice of thepresent invention for processing steel is a dispersion of graphite inwater or other suitable liquid medium. The lubricant is applied in anamount suffi cient to form a coating on the workpiece 10.

Following application of the lubricant, the workpiece is heated to anelevated temperature to remove the water or other inert liquid medium ofthe lubricant to form a fine graphite lubricant coating on the workpieceand to elevate the temperature of the workpiece to the initial workingtemperature. The workpiece is normally heated to a temperature in excessof 250 F. but below the lower critical temperature of the metal forsteel workpieces. As will be appreciated by those skilled in the art,the sequence of lubrication and heating shown in FIG. ll can be reversedwith the step of heating followed by lubrication to produce a hot,lubricant-coated workpiece.

Thereafter, the warm or hot wire having the fine graphite coating on thesurface is passed through the lead die 22 which can be a conventionaldie formed of a support and a nib 32. As indicated above, the lead die22 not only supports the workpiece for subsequent processing, but alsoserves to round and size the warm or hot workpiece and impart desirableproperties to the workpiece.

Rounding and sizing of the workpiece is advantageous for at least tworeasons. First, because all commercial hot-rolled rod or wire exhibitsome out-ofroundness and because the surface defects are most frequentlylocated on the workpiece about the periphery of the cross-section,rounding and sizing minimize the scrap generated and insure removal ofall defects. For example, if a workpiece had an oval or ellipticalcross-section, without rounding and sizing the cutting or shaving toolwould have to be dimensioned to remove the necessary amount of metalfrom the minor axis of the ellipse, thereby resulting in the removal ofexcess metal from the major axis of the workpiece and excess scrap.

Secondly, it has been found that rounding and sizing provides improvedtool life of the cutting or shaving tool. Because the feed affects toollife, control in the depth of cut results in uniform wear on thecircumference of the cutting or shaving tool and substantially minimizespremature failure of the cutting tool due to non-uniform loading of thecutting tool.

It has been found that the guiding function of the lead die insuresthat, once the workpiece is round, surface removal by the cutting orshaving tool occurs coaxially with the workpiece, thereby providing morecomplete surface defect elimination. In addition to its function as aguide, the lead die also serves to remove kinks and sharp bends from theworkpiece by reason of the working of the metal workpiece in the die andthe tension exerted on the workpiece by the die.

The lead die also serves to impart improved mechanical and physicalproperties to the workpiece by the plastic deformation of the workpiecein the die.

After passage through the lead die, the warm or hot workpiece is thenadvanced through a cutting or shaving tool 24 which operates to removeundesirable surface defects, such as seams, laps, slivers anddecarburization from the workpiece. As is shown more clearly in FIG. 2of the drawing, the cutting tool 24 completely encircles the workpiecefor removal of a surface layer or chip 36 form the workpiece.

It is important to the practice of the present invention that thetemperature of the workpiece, or at least the metal to be removed be ata temperature above 250F but below the lower critical temperature of themetal for steel workpieces, and that the temperature of the metal to beremoved be near or within the hot working temperature during removal ofthe metal to, prevent or minimize the build-up of strain hardened metalon the shaving edge of the cutting or shaving tool. The additional heatrequired to raise the metal being removed to a temperature near orpreferably within the hot working region of the metal is convenientlysupplied by the work performed during removal of surface metal from theworkpiece.

As will be appreciated by those skilled in the art, the heat build-upsupplied by work performed depends upon the linear rate at which theworkpiece is advanced through the shaving tool. Depending upon theamount of heat supplied by the heating means 18 and 20, it has beenfound that linear speeds of 10 to 350 feet/minute are sufficient toprovide the necessary heat to'raise the temperature of the metal beingremoved hear or within the working region for the metal.

The geometry of the cutting or shaving tool is important. For bestresults, use is preferably made of a tool having a rake angle of +20 to20 and a clearance angle of+l 5 tol5.

After'passage through the cutting tool 24, the workpiece 10 is againsprayed with a graphite-water dispersion lubricant by way of sprayer 26to again coat the surface of the workpiece with graphite. Because theworkpiece is at an elevated temperature, the workpiece is again coatedwith fine graphite which serves as a lubricant during subsequentprocessing. Application of the lubricant to the workpiece immediatelyafter passage through the cutting tool 24 also serves to cool theworkpiece and substantially eliminate undesirable oxide formation on thesurface of the workpiece which would otherwise form as a result of thehigh temperature of the workpiece.

The workpiece having the thin graphite coating thereon is then passedthrough a finish die which serves to guide the workpiece, size andpolish the workpiece and impart the finish properties to the workpiece.The guiding function is similar to that of the lead die. Thus, the leadand finish dies support the workpiece such that it is maintained coaxialwith the cutting tool to insure a uniform depth of cut and an improvedtool life.

The finish die is a reduction die and imparts the dimensions of thefinal product. The finish die also serves to polish the workpiece andcontributes to the working of the heated workpiece to provide anincrease in mechanical and physical properties, such as tensilestrength, yield strength and hardness.

The foregoing tools can be conveniently mounted on a suitable holdingfixture for attachment to a wire drawing block, a drawbench or the like.It is important that proper spacing be maintained between (a) the leaddie 22 and the cutting tool 24, and (b) the cutting tool 24 and thefinish die 30. As will be appreciated by those skilled in the art, theprecise distances depend on the grade, size and percent reduction ofeach tool. For most applications, a distance of 2 to 30 inches betweenthe lead die and the cutting tool, and a distance of 2 to 30 inchesbetween the cutting tool and the finish die, provide the best results.

The concepts of the present invention are applicable to a variety ofmetals, and particularly strain hardened steels such as hot rolledcarbon steels, hot rolled alloy steels, tool steels and the like. It hasbeen found that the process of the invention is particularly well suitedfor the finishing of patent wire to provide a significantly improvedsurface finish.

Having described the basic concepts of the invention, reference is madeto the following example which is provided by way of illustration, andnot of limitation, of the practice of the invention.

EXAMPLE This example illustrates the surface finishing of C-l04l steelcold heading wire in accordance with the process described in thisinvention.

One coil of hot rolled wire (Heat No. L424) was employed. This coil hada diameter of 7/16 inch (0.431

inch i X 10 and the following chemical analysis:

s Si 0.021 0.19

Mg P Ni 0.36 1.5 0.012 0.10

Inspection of this coil revealed that it had maximum partialdecarburization of 0.003 inches, intermittent seams less than 0.004inches in depth and the following mechanical properties:

Tensile I05 .000 psi Yield Elongation Red. of Area 59,000 psi I Lead die0.405/.406 Cutter 0.39l/.392 Finish die O.374/.375

The finished product had the following characteristics:

Scans and Decarburization None Finish Size 0.375 0.000

0.002 Hardness 30 to 32 Re Microfinish Less than l5 p-inches This coilbroached normally and the finished product was free of surface defectssuch as barber-poling and tearing or fish scaling. The mechanicalproperties were as follows:

Red. of Area Tensile Yield Elongation l 5 l .000 psi 1 28,000 psi 7% Inaddition, the workpieces treated in accordance with the presentinvention have been found to have improved formability. Formability canbe determined by subjecting a sample of the treated workpiece tocompression whereby the formability can be expressed as the ratio of theinitial height of the sample to the final height of the sample.

While not equivalent to the practice of the invention as describedabove, it has been found that it is possible, and sometimes desirable,toemploy the cutting tool used in the practice of the invention incombination with one of a lead die or a finish die. In the practice ofthis concept the die through which the workpiece is advancedis either inadvance of or subsequent to the cutting tool, and serves to work theworkpiece and impart thereto improved mechanical and physicalproperties, and serves to guide the workpiece for advancement throughthe cutting tool.

Whether the die precedes or follows the cutting tool, it is preferableto apply lubricant to the workpiece before passage through the cuttingtool as illustrated in FIG. 1.

It will be apparent that various changes and modifications can be madein the details of procedure and use without departing from the spirit ofthe invention, especially as defined in the following claims.

We claim:

1. A process for the surface finishing of metals comprising the steps ofpassing a metal workpiece of repeating cross-section coated with alubricant and heated to a temperature in excess of 250F through a firstdie to size and work the workpiece, passing the workpiece through acutting tool to effect removal of surface metal from the workpiece withthe temperature of the metal being removed being near the hot workregion of the metal, applying a lubricant to the workpiece to form acoating thereon, and passing the workpiece through a second die to workthe workpiece, with the first and second dies and the cutting tool beingin axial alignment.

2. A process as defined in claim I wherein the lubricant is graphite.

3. A process as defined in claim 1 wherein the lubricant is a suspensionof graphite in water.

4. A process as defined in claim 1 wherein the workpiece is heated to atemperature above 250F but below the critical temperature.

5. A process as defined in claim 1 wherein the workpiece is passedthrough the cutter at a rate sufficient to raise the temperature of themetal being removed to a temperature within the hot working region ofthe metal.

6. A process as defined in claim 1 wherein the workpiece is processed ata rate of 10 to 350 feet per minute.

7'. A process as defined in claim ll wherein the cutting tool has a rakeangle of +20 to 20 and a clearance angle of +l5 to l5.

8. A process as defined in claim ll wherein the first die is spaced fromthe cutting tool by 2 to 30 inches.

9. A process as defined in claim I wherein the second die is spaced fromthe cutting tool by a distance of 2 to 30 inches.

10. A process as defined in claim ll wherein the workpiece is a strainhardenable steel.

ill. In a process for the surface finishing of metal wherein a metalworkpiece of repeating cross-section heated to a temperature of at least250F and coated with a lubricant is passed through a cutting tool toremove surface metal, the improvement comprising pass ing the workpiecethrough at least one of a lead die preceding the cutting tool and afinish die following the cutting tool to work the metal and support theworkpiece as it is passed through the cutting tool.

l2. A process as defined in claim 111, wherein the metal is steel.

13. A process as defined in claim ill, wherein the lubricant isgraphite.

M. A process as defined in claim 11, wherein the workpiece is passedthrough the cutting tool at a rate sufficient to raise the temperatureof the metal being removed to a temperature within the hot workingregion of the metal.

2. A process as defined in claim 1 wherein the lubricant is graphite. 3.A process as defined in claim 1 wherein the lubricant is a suspension ofgraphite in water.
 4. A process as defined in claim 1 wherein theworkpiece is heated to a temperature above 250*F but below the criticaltemperature.
 5. A process as defined in claim 1 wherein the workpiece ispassed through the cutter at a rate sufficient to raise the temperatureof the metal being removed to a temperature within the hot workingregion of the metal.
 6. A process as defined in claim 1 wherein theworkpiece is processed at a rate of 10 to 350 feet per minute.
 7. Aprocess as defined in claim 1 wherein the cutting tool has a rake angleof +20* to -20* and a clearance angle of +15* to -15*.
 8. A process asdefined in claim 1 wherein the first die is spaced from the cutting toolby 2 to 30 inches.
 9. A process as defined in claim 1 wherein the seconddie is spaced from the cutting tool by a distance of 2 to 30 inches. 10.A process as defined in claim 1 wherein the workpiece is a strainhardenable steel.
 11. In a process for the surface finishing of metalwherein a metal workpiece of repeating cross-section heated to atemperature of at least 250*F and coated with a lubricant is passedthrough a cutting tool to remove surface metal, the improvementcomprising passing the workpiece through at least one of a lead diepreceding the cutting tool and a finish die following the cutting toolto work the metal and support the workpiece as it is passed through thecutting tool.
 12. A process as defined in claim 11, wherein the metal issteel.
 13. A process as defined in claim 11, wherein the lubricant isgraphite.
 14. A process as defined in claim 11, wherein the workpiece ispassed through the cutting tool at a rate sufficient to raise thetemperature of the metal being removed to a temperature within the hotworking region of the metal.